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In recent years there has been a growing debate about what proportion of the oceans is fished, with estimates ranging from well above 50% to just 4%. A new paper now looks at one of the most widespread and damaging fishing types, trawling, where a net is dragged over the sea bottom to capture fish. The new method focuses on shallower continental shelves that are less than 1000 m in depth, finding that the trawling footprint varies hugely across regions from 0.4% of the area to more than 80%, with an average of 14% for all regions examined.

A new analysis that uses high-resolution data for 24 ocean regions in Africa, Europe, North and South America and Australasia shows that 14 percent of the overall seafloor shallower than 1,000 meters (3,280 feet) is trawled. Most trawl fishing happens in this depth range along continental shelves and slopes in the world’s oceans. The study focused on this depth range, covering an area of about 7.8 million square kilometers of ocean.

Many fisheries around the world are not formally assessed, and for these fisheries it is hard to know whether they are overfished or not, and how much to fish to ensure that fishing remains sustainable. A suite of models has been developed that can be applied to fisheries where the only data available are time series of catches, but there is no information on trends in actual fish numbers.

Marine fisheries management aims to keep fish populations at sustainable levels while producing seafood. Fisheries that are assessed to be overfished must have their populations rebuilt to sustainable levels by reducing catches to lower levels. Usually the assessment of status relies on a complicated fisheries stock assessment model, sort of like a weather forecast for fisheries, that estimates the level of sustainable catch that can be taken from a fisheries population.

Bull trout use a bewildering array of strategies to aid in their survival, from remaining in streams their whole lives, like rainbow trout, to spending part of their lives in the ocean before returning to streams to spawn, just as salmon do. Bull trout are present in only one of two neighboring rivers in the Olympic peninsula, Washington state, and in this one (the Elwha River), two large dams were removed during the period 2011-2014.

For decades, fish researchers believed in Gerking’s “restricted movement paradigm”, thinking that river-dwelling fish largely stay in the same place and rarely venture forth. But in recent decades, ecologists have harnessed the power of both advanced tags and improved genetic methods to directly estimate movement distances and average home ranges of different fish species. Now, a new paper has gathered in one place data from more than 200 direct movement studies and more than 200 genetic studies to estimate how far river fish more on average.

The U.S. Endangered Species Act has saved or recovered many species, and is recognized as one of the most powerful laws in the world for protecting the environment. The primary aim of the Act is to ensure that populations and species persist, and to conserve genetic variation in population. But little attention is paid to the adaptive potential of populations—the capability of populations to evolve when faced with new selective pressures—even though new genetic methods of sequencing the entire DNA of organisms are now cheaper and easier than ever before.

To protect and recover species, most countries have laws that mandate particular actions when species are classified as threatened or endangered. These classifications can have an enormous impact on industries that impinge on the species in question, for example the declaration of northern spotted owls as endangered led to large-scale shutdowns in logging on old-growth forests. This process of classifying a species as threatened, endangered, or neither constitutes a difficult decision, and difficult decisions can usefully be approached using the theory and tools of decision analysis.

A new and more accurate study reveals that about 4% of the ocean area experiences fishing each year, a far smaller estimate than previous studies that relied on very large grid sizes. Two recent studies estimated that fishing takes place in 55% of the ocean and 90% of the ocean each year. But these estimates divide the ocean into 0.5°×0.5° grid cells, which are ~3100 km² in size at the equator, and assume each cell is fished if a single fishing location is recorded in the entire cell.

Whooping Cranes are highly endangered. To improve their recovery chances, a new migratory population was reintroduced into the wild in 2001, but their hatching success has been very low. A new study examines three possible hypotheses for this failure: harassment by black flies of nesting birds, effects of captive rearing, and inexperience of breeding birds. The overwhelming finding was that black fly harassment is the cause of poor hatching success: for example, when black fly numbers were reduced experimentally, breeding success doubled.